Terry,You're right, Max Penetration does have to do with the maximum depth a tool will cut-- per pass. If you specify it as 1/2", the machine will make 1/2" passes until it reaches the material thickness you specified. I do believe you can leave a skin, BUT our operator has been experiencing some difficulty with this. For instance, if he wants to cut 2" in 1/2" steps and leave a 1/8" skin, it cuts four 1/2" passes (all the way through) and then retracts to leave the skin, which has already been cut through. I'm not sure what his fix was at this point, I think he just added the skin thickness to the spoilboard thickness. I think he also tried using 1-7/8" divided by 4 as his max pen depth instead of 2" divided by 4. I haven't discussed this with him in a few days, but I know he doesn't cut any 2" solid without first running the program in the air. I'll get more info from him on Monday and post an update.